Due to the pressure at this point, you can't just glue up the crack and tune the strings back up. It requires a full belly-off repair job.
This is the soundpost crack – going off in three directions. i glued this up first.
Then I carve away a dome-shaped area on the rear of the plate, almost all the way through to the varnish!
I rub pink chalk into the polished cavity, then press the pre-cut patch wood into the space. Wherever it shows pink, I remove wood, and repeat until the whole surface is contacting evenly and closely.
in the next pic you can just see the back of the crack peeping through. the belly is now about 2mm thick in the middle.
for clamping, i've improvised a miniature go-bar deck. I prefer this way to using c clamps and it allows me to apply pressure where and how i want.
The finished patch; for this lower-priced bass it'll do the trick and get the bass back playing again.
